module sun_mod

  use const_mod

  implicit none

  private

  public sun_init
  public solar_zenith_angle

  type orbit_type

  end type orbit_type

  type(orbit_type) orbit

contains

  subroutine sun_init(planet)

    character(*), intent(in) :: planet

    select case (planet)
    case ('earth')

    case ('mars')

    end select

  end subroutine sun_init

  real(r8) function solar_zenith_angle() result(res)

  end function solar_zenith_angle

end module sun_mod
